Well is possible to remove the flickering by adding the animation to the first backdrop only.

Anyway, if we are going to remove this class, we should stop adding them to the Dialogs too, by removing the code that does it in `src/widgets/Dialogs.js`. https://github.com/adobe/brackets/blob/master/src/widgets/Dialogs.js#L298 and 
https://github.com/adobe/brackets/blob/master/src/widgets/Dialogs.js#L322 and https://github.com/adobe/brackets/blob/master/src/widgets/Dialogs.js#L336